Pressures on pollinators, responses and action

The threat of the collapse in pollinating insect populations is confirmed as a worldwide problem according to the latest meta-review of research literature.

Threats to an ecosystem service: Pressures on pollinators by AJ Vandenburg and his co-authors was published today in the April 22 edition of Frontiers of Ecology and Environment. The paper comes after recent House of Commons Environment Select Committee criticism of the UK Minister for Environment who had argued that there was insufficient evidence of the impact of systemic insecticides (neonicotinoids) on Honey bees to justify measures to restrict their use.

This latest research, emanates from the UK’s Centre of Hydrology and Ecology, it highlights the multiple pressures on insects which by impacting on the productivity of agricultural and natural plants are likely to have profound effects on the environment, on human health and on economic activity (75% of Crops worldwide are pollinated by insects as are 94 percent of wild flowering plants).

Among its overall conclusions the paper highlights that even if domestic bees were not affected by the same issues it would be impossible to use them to significantly replace the pollination services agricultural systems gain from native insect species such as wild bees, flies, butterfly and moths . It identifies the principal drivers of decline as, habitat and land use change leading to reduction in natural variety and seasonal availability of food plant species; agro-chemical impacts, particularly biocides; and the spread of pests and pathogens.

As with several papers on the issue recently the scientist’s have put much energy into highlighting areas of uncertainty and recommending more research, which of course keeps scientists busy. The paper highlights no single smoking gun and instead points to the complexity of the issues in the field where for example changes that are very negative for one pollinator, such as the introduction for of a new crop, may be beneficial to another. However it also highlights that the individual threats are likely to combine and exacerbate negative impacts.

The paper does also offer some ‘perspectives for decision making’. The first highlights that land management practices which encourage landscape integrity, biodiversity and ecological networks to provide for the breeding and feeding needs for pollinators are significant. This concurs with the policy emphasis in the England White Paper on Environment which emphasises the importance of landscape level ecology and improving ecological networks. So this approach in the UK at least has policy support and there are many options which could be pursued to help mitigate against the loss of breeding and feeding resources. Such actions are already encourages through initiatives such Conservation Grade Farming which encourages the set aside and reserving of field boundaries to support pollen and nectar rich wild flowers.

The paper also highlights the need for insect disease management on multiple fronts – pointing out understanding the host and pathogen relationship and the role of vectors across many species is not trivial. This is an area where significant ongoing research will be needed with perhaps incremental potential for improvements over the longer term, however this seems to be insufficient alone to significantly reverse current trends.

This brings us on to the third area, the question of agro-chemical risks. While the paper does not point to pesticides and neonicotinoid varieties as the primary cause it gives no support for the status quo and inaction. It highlights that current pesticide application guidelines are intended to minimise lethal impacts on honey bees but do not necessarily protect other pollinators with different physiologies, behaviours and phenologies. This is significant as less than 12% of UK crops are estimated to be actually pollinated by honey bees, by far the greater part of the pollination of commercial crops is actually carried out by wild insect species. Clearly reducing pesticide impacts on them would be a a highly effective strategy for protecting pollination services.

Furthermore much of the insecticide testing has not looked significantly at sub-lethal impacts. There is evidence that low doses for example impact bee learning and hence foraging behaviours, which would effectively reduce the energy accessible to the hive and its social organisation. Similarly there has been limited research on such issues as sub-lethal impact on insect immune and reproductive systems or for example o reproductive success. It would be rather unusual if ‘sub-lethal doses’ (chronic poisoning) did not produce effects (for example DDT, before it was banned, had massive impacts on birds not just through adult mortality but through the thinning of bird egg-shells which significantly lowered reproductive success).

So while the paper does not point a smoking gun at biocides it does strongly point to minimising their impacts. There are a variety of options for this including seeking to implement alternative approaches such as biological and integrated methods of control and, rather than routine precautionary applications, improve the level of pest monitoring in the field and use pesticide responses only as a necessary resort. Specific issues and potential in this areas were highlighted in my February report on potential benefits of better integrated pest management over pesticide dependent systems. This highlights that there are options which would make pesticides a less significant factor in the pollination services equation – the main issue is political will.

3 responses to “Pressures on pollinators, responses and action”

It is always refreshing to read a balanced article based upon consideration of the available science. When will we learn from pass mistakes and use the knowledge to wisely support our technological future?